The Assisted Suicide Bill will be scrutinised by MSPs before parliament is asked to vote on it
Legal experts and the police said a law allowing assisted suicide in Scotland needed more clarity in order to remove the risk of someone being prosecuted.
There is a “fine line” between assisting someone killing themselves and an act of euthanasia which could result in criminal charges, MSPs heard.
The plans, contained in a backbench bill, have widespread public backing, said supporters.
But opponents believed such a move was “unethical and uncontrollable”.
The Scottish government does not support a change in the law.
The Assisted Suicide Bill would give people whose lives have become intolerable through a progressive degenerative condition or terminal illness the right to seek the help of a doctor to help end their lives.
The legislation, which has begun its passage through parliament, says the final act must be carried out by the person seeking to end their own life.
But Prof Alison Britton, of the Law Society of Scotland, said a definition of assisting suicide was needed, especially in cases where someone had become too ill to end their life.
Assisted Suicide – The Legal Position
Guidance on assisted suicide in England, Wales and Northern Ireland was issued after the Debbie Purdy case
It is not illegal to attempt suicide in Scotland, but helping someone take their own life could lead to prosecution.
In England and Wales, the Suicide Act 1961 makes it an offence to encourage or assist a suicide or a suicide attempt, which is almost identical to the situation in Northern Ireland.
The Director of Public Prosecutions has to approve any assisted suicide court action in England, Wales and Northern Ireland.
In 2010, Keir Starmer, then the DPP, issued guidance that made it clear that family or friends who travelled with a loved one to the Swiss suicide group Dignitas would not risk prosecution.
The guidelines were the result of a case brought by Debbie Purdy, a terminally ill woman, who in 2009 won a legal ruling requiring the DPP to set out whether her husband would be committing an offence if he accompanied her to Dignitas to end her life.
Scotland’s prosecution service, the Crown Office, has issued no such guidance.
Assisted suicide is legal in Luxembourg, the Netherlands and Belgium as well as Switzerland.